A mobile phone, a digital AV device, an IC card, and the like have higher functions. This increases a demand for having a higher density chip inside a package by reducing a size and a thickness of a semiconductor silicon chip (hereinafter, referred to as a chip) to be mounted on these devices. In order to have the higher density chip inside the package, the thickness of the chip should be reduced so as to be within a range from 25 μm to 150 μm.
However, if a semiconductor wafer (hereinafter, referred to as a wafer), which is a base of the chip, is ground and thereby reduces its thickness, the wafer reduces its strength and is apt to have a crack or to be curved. The wafer whose strength has been reduced due to the reduction in its thickness is difficult to be conveyed in an automated manner. Instead, such the wafer should be conveyed manually by a person. This gives the person troublesome procedures.
In view of this, a wafer supporting system has been developed. According to the wafer supporting system, a so-called support plate, which is made of materials such as glass and hard plastic, is bonded to a wafer which is to be ground. This allows the wafer to maintain its strength, thereby preventing the wafer from having a crack or being curved. Because the wafer supporting system allows a wafer to maintain its strength, it is possible to convey, in an automated manner, a semiconductor wafer whose thickness has been reduced.
The wafer and the support plate are bonded to each other by means of adhesive tape, a thermoplastic resin, an adhesive, or the like. Before the wafer is subjected to dicing, the support plate is separated from a substrate. In a case where the wafer and the support plate are bonded to each other by means of the adhesive tape, the wafer is separated from the support plate by ripping out the support plate from the wafer. In a case where the wafer and the support plate are bonded to each other by means of the thermoplastic resin, the wafer is separated from the support plate by heating and melting the resin. In a case where the wafer and the support plate are bonded to each other by means of the adhesive, the wafer is separated from the support plate by means such as dissolving the adhesive by using a dissolving solution.
Before the support plate is separated from the wafer in the manner as described above, a side of the wafer which side is not bonded to the support plate is bonded to another support member such as a dicing tape, depending on a thickness of the wafer. This is necessary because the wafer has a low strength due to its small thickness and thereby is apt to have a crack. That is, a laminate is once formed by a dicing tape, a substrate, and a support plate, and then the support plate is separated from the substrate.
Japanese Unexamined Patent Application Publication, Tokukai, No. 2006-135272 (published on May 25, 2006) discloses such an arrangement that (i) a wafer and a support plate are bonded to each other by means of an adhesive, (ii) the adhesive is dissolved by using a dissolving solution, and (iii) the support plate is separated from the wafer. In this publication, the support plate bonded to the wafer has a through-hole, through which the dissolving solution is supplied to the adhesive, and then the wafer is separated from the support plate.